Metal coated recording medium for recording instruments



E. TRAUB 2,687,361

Aug. 24, 1954 METAL COATED RECORDING MEDIUM FOR RECORDING INSTRUMENTS Filed Nov. 13, 1950 'unllnlluallllllllllllllllllll L .r11 u l, uanunrlunu 'laIl11111111llllllilnunuunuulluullua /NVE/VTOR Eberhczfdz Waub Patented Aug. 24, 1954 METAL COATED RECORDING MEDIUM FOR RECORDING INSTRUMENTS Eberhardt Traub, Stuttgart, Germany, assignor to Robert Bosch G. m. b. H., Stuttgart, Germany Application November 13, 1950, Serial No. 195,373

1 claim. 1

The invention relates to metal coated recording mediums, such as dielectric recording strips to which, for instance, the metal coating can have been applied by evaporation. Recording strips of this type are preferably used in recording instruments recording readings of measuring instruments by having an electrical stylus burn a trace into the metallized coating of the recording strips.

The object of the invention is to increase the life of the metal coating and to prevent its premature deterioration. Premature failure of the metal coating has, for instance, been noticed on dielectric strips with an evaporated zinc coating, which were found to be unsatisfactory due to disintegration of the metal.

As research has shown that the disintegration of the'metal is primarily due to chemical action caused by water absorbed by the hygroscopic paper to which the metal is applied, the present invention therefore provides that the to be metallized surface of the recording strip or both its surfaces be coated with nonhygroscopic, chemically neutral material.

Such a recording strip can, for instance, be made of paper, one surface of which has been varnished and then been coated with metal applied by evaporation. When storing such recording strips in rolls the metallized coating of one winding will be in contact with the non-metallized back of the next Winding and will, thus, be exposed to corrosive action. It will, therefore, be found expedient to varnish both sides of the paper strip prior to metallizing its top surface. it is, of course, also possible to replace the paper strips With strips made Wholly of chemically neutrai and nearly nonhygroscopic material such as polystyrene.

It has further been found that the life of the metal coatings also depends on the selection of the coating metal. Cadmium applied by evaporation has been found to form the most stable metal coating. Cadmium coated recording mediums have retained their serviceableness for many years.

The object of the invention is illustrated by way of example in the accompanying diagrammatic drawing which shows a sectional View of a paper strip I having a varnish coating 2 applied to both its surfaces. The cadmium coating 3 has been applied by evaporation to one of the varnish coatings 2. The drawing does not correspond to actual conditions. Actually the thickness of the paper is 15-20 a the thickness of the varnish coating 0.8-1 a and the thickness of the metal coating 0.05-01 e.

What I claim is:

A strip for electrical recording comprising, in combination, a strip consisting of hygroscopic material, said strip having two faces arranged 0pposite to each other; a layer consisting of nonhygroscopic material and being superposed to one of said faces of said strip, said non-hygroscopic layer having a thickness of between .8 and 1 u; and a cadmium layer superposed to said nonhygroscopic layer, said cadmium layer having a thickness of between .05 and .1 a.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,274,444 Freed Feb. 24, 1942 2,382,432 McManus et al. Aug. 14, 1945 

